Devices exist to atomize and dispense liquids. These include liquid dispensers, medical devices, printing devices and many more. Pressurized aerosol canisters and hand-operated sprayers are the most common devices in use. Pressurized devices have environmental concerns related to volatile emissions and are also limited by precision metering of liquids, cost and power consumption.
Piezoelectric ultrasonic vaporization devices have been developed to increase precision, especially for printing and medical device applications. Some devices, such as used in a humidifier, are less precise and work only with certain types of liquids.
Other piezoelectric ultrasonic devices for liquid dispensing use a vibrating membrane and a wick to deliver liquid to the vibrating membrane. The wick limits the range of liquids to be used in these devices because of clogging of the wick and limitations of the viscosity of the liquid. The vertical orientation of a wick further restricts the design because it requires that the orientation of the vibrating membrane be horizontal. Further, the vibrating membrane in such devices is sensitive to residual accumulation of liquid on the plate. This reduces the range of liquids that can be used in such a device. Finally, the reservoir size that can be used in such a device is relatively small, because its height is limited by the height that a wick can draw liquid to the vibrating membrane.
Devices used to dispense ink for printing employ a chamber pressurized from the back to eject droplets through a perforated membrane. These designs are appropriate for Inkjet printing but are relatively expensive because they require precise semiconductor fabrication processes. In such designs, the delivery of liquid to the perforated membrane is a challenge and only small volume reservoirs can be used.